There is growing demand for a method and apparatus for treating only one side of a strip product. For example, manufacturers are seeking a strip product wherein one side is corrosion resistant and the other side is such that a good paint finish may be applied thereto. One example of such a product is a steel strip coated on only one side with zinc for corrosion resistance while the other side of the strip may be painted.
A number of methods to produce a one sided, zinc coated steel strip have been proposed. Such methods include (1) applying a material to the strip which prevents one side of the strip from accepting the zinc, (2) coating both sides of the strip and thereafter removing the coating from one side, (3) utilizing vacuum deposition or electrolytic coating to apply a coating to one side of the strip, and (4) welding two strips of steel together, passing the double thickness through a coating step and thereafter separating the two strips.
All of the above proposed methods have one or more of the following disadvantages: high operating costs, significant investment in new equipment or substantial departure from existing two side coating operations.